Powder clearcoat dispersions (powder slurry clearcoats), method for producing them and the use thereof

ABSTRACT

Powder clearcoat dispersions (powder slurry clearcoats) preparable by dispersing a powder clearcoat in an aqueous medium and wet milling the resulting powder slurry, at least one adduct of ethylene oxide and/or propylene oxide with at least one glycol being added to the powder slurry prior to wet milling; and the use of the powder slurry clearcoats for producing clearcoat finishes, especially as part of multicoat color and/or effect finishes.

[0001] The present invention relates to powder clearcoat dispersions(powder slurry clearcoats). The present invention further relates to anovel process for preventing surface defects in clearcoat finishes. Thepresent invention relates, moreover, to the use of the novel powderslurry clearcoats in automotive finishing, in the interior and exteriorcoating of constructions, in furniture, door and window coating and inindustrial coating, including coil coating and container coating.

[0002] Color and/or effect finishes on motor vehicle bodies, especiallyautomobile bodies, nowadays consist preferably of two or more coatswhich are applied on top of one another and have different properties.

[0003] For example, a substrate has applied to it, in succession, anelectrodeposition coating (EDC) as primer, a surfacer coat orantistonechip primer, a basecoat, and a clearcoat. The particularpurpose of the EDC is to protect the metal panel against corrosion. Inthe art it is also commonly referred to as the primer. The surfacer coatserves to cover over unevennesses in the substrate and, by itselasticity, to ensure stone-chip resistance. If desired, the surfacercoat may also act to reinforce the hiding power and to deepen the colorof the coating system.

[0004] The base coat contributes the colors and/or optical effects. Theclearcoat is used to intensify the optical effects and to protect thecoating system against mechanical and chemical damage. Basecoat andclearcoat are often also referred to collectively as the topcoat. Forfurther details, reference is made to Römpp Lexikon Lacke undDruckfarben, George Thieme Verlag, Stuttgart, New York, 1998, pages 49and 51, “Automotive finishes”.

[0005] An important objective in modern automotive finishing issignificantly to reduce, or do away altogether with, the amount oforganic solvents released in the course of the coating operation.Appropriate coating materials, such as EDCs, aqueous surfacers oraqueous clearcoats, powder coating materials or powder slurryclearcoats, are available.

[0006] Of these, the powder slurry clearcoats, which are known, forexample, from U.S. patents U.S. Pat. No. 4,268,542 A1 and U.S. Pat. No.5,379,947 A1 and from the Patent Applications EP 0 714 958 A2, DE 195 40977 A1, DE 195 18 392 A1, DE 196 17 086 A1, DE-A-196 13 547, EP 0 652264 A1, DE 196 18 657 A1, DE 196 52 813 A1, DE 196 17 086 A1, DE 198 14471 A1 and DE 198 35 206 A1, offer particular advantages: firstly, theycan be prepared and applied without solvent, like the powder coatingmaterials; secondly, the customary and known spraying techniques forliquid coating materials may be employed for their application.

[0007] A disadvantage of the powder slurry clearcoats known to date isthat the clearcoat finishes produced therefrom in some cases havesurface defects such as depressions, craters and agglomerates, whichdetract from the otherwise excellent overall visual impression. Nor hasit been possible to date entirely to eliminate this problem by addingadditives such as wetting agents, emulsifiers, dispersing auxiliaries ordefoamers during the preparation of the powder slurry clearcoats.

[0008] It is an object of the present invention to find new powderclearcoat dispersions (powder slurry clearcoats) which, like the powderslurry clearcoats known to date, provide clearcoat finishes with anexcellent overall visual impression and high scratch, chemical andweathering resistance but without surface defects such as depressions,craters or agglomerates.

[0009] Accordingly, the novel powder clearcoat dispersions (powderslurry clearcoats) have been found, which may be prepared by dispersinga powder clearcoat in an aqueous medium and wet milling the resultingpowder slurry, at least one adduct of ethylene oxide and/or propyleneoxide with at least one glycol being added to the powder slurry prior towet milling.

[0010] In the text below, the novel powder clearcoat dispersions orpowder slurry clearcoats are referred to as “powder slurry clearcoats ofthe invention”. Further subject matter of the invention will emerge fromthe following description.

[0011] In the light of the prior art it was surprising and unforeseeableby the skilled worker that the use, in accordance with the invention, ofadducts of ethylene oxide and/or propylene oxide with glycols wouldresult in powder slurry clearcoats which provide clearcoat finishes withan excellent overall visual impression and high scratch, chemical andweathering resistance but without surface defects such as depressions,craters or agglomerates.

[0012] The powder slurry clearcoats of the invention comprise at leastone finely divided dimensionally stable constituent, i.e., a powdercoating material, as the disperse phase, and an aqueous medium as thecontinuous phase.

[0013] The finely divided, dimensionally stable constituent or powdercoating material may be solid and/or highly viscous. In the context ofthe present invention, “highly viscous” means that the particles behaveessentially as solid particles under the customary and known conditionsof the preparation, storage and use of powder slurry clearcoats orpowder coatings. The powder coating material is preferably solid.

[0014] Furthermore, the individual particles of the finely dividedconstituent or powder coating material are dimensionally stable. In thecontext of the present invention, “dimensionally stable” means thatunder the customary and known conditions of the storage and use ofpowder slurry clearcoats and powder coatings the particles agglomerateand/or break down into smaller particles only to a small extent, if atall, but essentially retain their original form even under the influenceof shear forces.

[0015] The solids content of the powder slurry clearcoat of theinvention is preferably from 10 to 80, more preferably from 15 to 75,with particular preference from 20 to 70, with very particularpreference from 25 to 70, and in particular from 30 to 65% by weight,based in each case on the powder slurry of the invention.

[0016] The average particle size of the finely divided dimensionallystable constituents of the powder slurry clearcoat of the invention ispreferably from 0.8 to 40 μm, more preferably from 0.8 to 20 μm, andwith particular preference from 2 to 6 μm. By average particle size ismeant the 50% median value determined by the laser diffraction method,i.e., 50% of the particles have a particle diameter≦the median value and50% of the particles have a particle diameter≧the median value. Ingeneral, the particle size of the finely divided dimensionally stableconstituents reaches its upper limit when owing to their size theparticles are no longer able to flow out completely on baking, with theconsequence of an adverse effect on film leveling. 40 μm is considered asensible upper limit, since above this particle size blockage of therinsing tubes of the highly sensitive application apparatus is to beexpected.

[0017] Powder slurry clearcoats with average particle sizes of this kindpossess better application properties and, at the applied filmthicknesses of >30 μm as currently practiced in the automotive industryfor the OEM finishing of automobiles, surprisingly exhibit asignificantly reduced tendency toward popping and mudcracking thanconventional combinations of surfacer, basecoat, and clearcoat.

[0018] The powder slurry clearcoat of the invention is essentially freefrom organic solvents (cosolvents). In the context of the presentinvention, this means that the clearcoats have a residual volatilesolvent content of <5% by weight, preferably <3% by weight and withparticular preference <2% by weight, based on the overall weight of thepowder slurry clearcoat.

[0019] The constituent of the powder slurry clearcoats of the inventionthat is essential to the invention is at least one adduct of ethyleneoxide and/or propylene oxide with at least one glycol, especiallyethylene glycol, 1,3- and/or 1,2-propylene glycol or 1,2-, 1,3- and/or1,4-butylene glycol.

[0020] Examples of highly suitable adducts are polyethylene glycols,polypropylene glycols, block copolymers of ethylene oxide and propyleneoxide (Pluronics®) or polytetramethylene glycols (polytetrahydrofurans)(cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998,page 457, “Polyalkylene glycols”), of which the adducts of propyleneoxide with 1,3- and/or 1,2-propylene glycol, i.e. the polypropyleneglycols are particularly advantageous and are therefore used withparticular preference in accordance with the invention.

[0021] Particularly suitable polypropylene glycols have a number-averagemolecular weight of from 350 to 1000, preferably from 400 to 950, withparticular preference from 450 to 900, with very particular preferencefrom 500 to 850, and in particular from 550 to 800 daltons.

[0022] The polypropylene glycols are commercial products and aremarketed, for example, by BASF Aktiengesellschaft under the brand namePluriol® 400, 600 or 900, the numbers following indicating the molecularweight or its magnitude. Of these, Pluriol® 600 is especiallyadvantageous and is therefore used with particular preference inaccordance with the invention.

[0023] The amount of the adducts for use in accordance with theinvention in the powder slurry clearcoats of the invention is preferablyfrom 0.01 to 2.0, more preferably from 0.1 to 1.5, with particularpreference from 0.2 to 1.2, with very particular preference from 0.25 to1.0, and in particular from 0.3 to 0.8% by weight, based in each case onthe solids content of the powder slurry clearcoat of the invention.

[0024] Hereinbelow, the solids content is the sum of the constituents ofthe powder slurry clearcoat of the invention which, after curing,constitute the solids content of the clearcoat finish.

[0025] Surprisingly, the effect in accordance with the invention of theadducts described above may be intensified by means of small amounts ofsolvent having high solvency. By small amounts here are meant amounts offrom 0.1 to 1.9, preferably from 0.2 to 1.8, with particular preferencefrom 0.3 to 1.7, with very particular preference from 0.4 to 1.6, and inparticular from 0.5 to 1.5 parts by weight per 100 parts by weight ofsolids of the powder slurry clearcoat of the invention.

[0026] Suitable organic solvents are marketed, for example, under thebrand name Solvenon® (especially Solvenon® IPP, isopropoxypropanol) byBASF Aktiengesellschaft or under the brand name Solvesso® by Exxon/Esso.Of these, Solvenon® IPP is particularly advantageous and is thereforeused with particular preference.

[0027] The powder slurry clearcoats of the invention may be curablephysically, thermally, with actinic radiation, or thermally and withactinic radiation (dual cure). The thermally curable powder slurryclearcoats of the invention may in turn be self-crosslinking orexternally crosslinking.

[0028] In the context of the present invention, the term “physicalcuring” means the curing of a coat of a coating material by filmformation as a result of loss of solvent from the coating material, withlinking within the coating taking place by looping of the polymermolecules of the binders (regarding the term, cf. Römpp Lexikon Lackeund Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998,“Binders”, pages 73 and 74). Alternatively, film formation takes placeby way of the coalescence of binder particles (cf. Römpp Lexikon Lackeund Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998“Curing”, pages 274 and 275). Normally, no crosslinking agents arenecessary for this purpose. If desired, physical curing may be assistedby atmospheric oxygen, heat, or exposure to actinic radiation.

[0029] In the context of the present invention, the term“self-crosslinking” refers to the property of a binder to undergocrosslinking reactions with itself. The prerequisite for this is thatboth types of complementary reactive functional groups necessary forcrosslinking are already present in the binders. Externally crosslinkingcoating materials, adhesives and sealing compounds, on the other hand,are those wherein one kind of the complementary reactive functionalgroups is present in the binder and the other kind is present in acuring or crosslinking agent. For further details, reference is made toRömpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, NewYork, 1998, “Curing”, pages 274 to 276, especially 275, bottom.

[0030] In the context of the present invention, actinic radiationcomprises electromagnetic radiation, such as near infrared (NIR),visible light, UV radiation or x-rays, especially UV radiation, andcorpuscular radiation such as electron beams.

[0031] If thermal curing and curing with actinic light are employedconjointly, the terms “dual cure” and “dual cure powder slurryclearcoat” are also used.

[0032] The powder slurry clearcoats of the invention comprise at leastone binder.

[0033] The binders are oligomeric and polymeric resins.

[0034] In accordance with the invention it is of advantage if theminimum film-forming temperature of the binders is at least 0° C.,preferably at least 10, with particular preference at least 15, withvery particular preference at least 20, and, in particular, at least 25°C. The minimum film-forming temperature can be determined by drawingdown an aqueous dispersion of the binder onto a glass plate using acoating bar or applying a finely divided binder powder to a glass plateand heating it in a gradient oven. The temperature at which thepulverulent layer films is referred to as the minimum film-formingtemperature. For further details reference is made to Römpp LexikonLacke und Druckfarben, George Thieme Verlag, Stuttgart, New York, 1998,“Minimum film-forming temperature”, page 391.

[0035] Examples of suitable binders are random, alternating and/or blockaddition (co)polymers of linear and/or branched and/or comblikeconstruction of ethylenically unsaturated monomers, or polyadditionresins and/or polycondensation resins. For further details of theseterms reference is made to Römpp Lexikon Lacke und Druckfarben, GeorgeThieme Verlag, Stuttgart, New York, 1998, page 457, “Polyaddition” and“Polyaddition resins (polyadducts)”, and pages 463 and 464,“Polycondensates”, “Polycondensation” and “Polycondensation resins”, andalso pages 73 and 74, “Binders”.

[0036] Examples of suitable addition (co)polymers are (meth)acrylate(co)polymers or partially hydrolyzed polyvinyl esters, especially(meth)acrylate copolymers.

[0037] Examples of suitable polyaddition resins and/or polycondensationresins are polyesters, alkyds, polyurethanes, polylactones,polycarbonates, polyethers, epoxy resin-amine adducts, polyureas,polyamides, polyimides, polyester-polyurethanes, polyether-polyurethanesor polyester-polyether-polyurethanes, especiallypolyester-polyurethanes.

[0038] Of these binders, the (meth)acrylate (co)polymers have advantagesand are therefore used more frequently.

[0039] The self-crosslinking binders of the thermally curable powdercoating materials and powder slurry clearcoats and of the dual-curepowder coating materials and powder slurry clearcoats comprise reactivefunctional groups which are able to enter into crosslinking reactionswith groups of their type or with complementary reactive functionalgroups. The externally crosslinking binders comprise reactive functionalgroups which are able to enter into crosslinking reactions withcomplementary reactive functional groups present in crosslinking agents.Examples of suitable complementary reactive functional groups for use inaccordance with the invention are summarized in the following overview.In the overview, the variable R is an acyclic or cyclic aliphatic, anaromatic, and/or an aromatic-aliphatic (araliphatic) radical; thevariables R′ and R″ are identical or different aliphatic radicals or arelinked to one another to form an aliphatic or heteroaliphatic ring.

[0040] Overview: Examples of Complementary Functional Groups Binder andcrosslinking agent or Crosslinking agent and binder —SH —C(O)—OH —NH₂—C(O)—O—C(O)— —OH —NCO —O—(CO)—NH—(CO)—NH₂ —NH—C(O)—OR —O—(CO)—NH₂—CH₂—OH >NH —CH₂—O—R —NH—CH₂—O—R —NH—CH₂—OH —N(—CH₂—O—R)₂—NH—C(O)—CH(—C(O)OR)₂ —NH—C(O)—CH(—C(O)OR)(—C(O)—R) —NH—C(O)—NR′R″>Si(OR)₂

—C(O)—OH

—N═C═N— —C(O)—N(CH₂—CH₂—OH)₂

[0041] The selection of the complementary groups in each case is guidedfirstly by the fact that during the preparation, storage, application,and melting of the powder slurry clearcoats of the invention they shouldnot enter into any unwanted reactions, in particular no prematurecrosslinking, and/or, if appropriate, should not disrupt or inhibitcuring with actinic radiation, and secondly by the temperature rangewithin which crosslinking is to take place.

[0042] In the case of the powder slurry clearcoats of the invention,which are curable thermally or thermally and with actinic radiation, itis preferred to employ crosslinking temperatures of from 60 to 180° C.Use is therefore made preferably of thio, hydroxyl, N-methylolamino,N-alkoxymethylamino, imino, carbamate, allophanate and/or carboxylgroups, preferably hydroxyl or carboxyl groups, on the one hand, andpreferably crosslinking agents containing anhydride, carboxyl, epoxy,blocked isocyanate, urethane, methylol, methylol ether, siloxane,carbonate, amino, hydroxyl and/or beta-hydroxyalkylamide groups,preferably epoxy, beta-hydroxyalkylamide, blocked isocyanate, urethaneor alkoxymethylamino groups, on the other.

[0043] In the case of self-crosslinking powder materials and powderslurry clearcoats of the invention, the binders contain in particularmethylol, methylol ether, and/or N-alkoxymethylamino groups.

[0044] Complementary reactive functional groups especially suitable foruse in the powder coating materials and powder slurry clearcoats of theinvention are

[0045] carboxyl groups on the one hand and epoxide groups and/orbeta-hydroxyalkylamide groups on the other, and

[0046] hydroxyl groups on the one hand and blocked isocyanate, urethaneor alkoxymethylamino groups on the other.

[0047] The functionality of the binders in respect of the reactivefunctional groups described above may vary very widely and depends inparticular on the desired crosslinking density and/or on thefunctionality of the crosslinking agents employed in each case. In thecase of carboxyl-containing binders, for example, the acid number ispreferably from 10 to 100, more preferably from 15 to 80, withparticular preference from 20 to 75, with very particular preferencefrom 25 to 70, and, in particular, from 30 to 65 mg KOH/g.Alternatively, in the case of hydroxyl-containing binders, the OH numberis preferably from 15 to 300, more preferably from 20 to 250, withparticular preference from 25 to 200, with very particular preferencefrom 30 to 150, and in particular from 35 to 120 mg KOH/g.Alternatively, in the case of binders containing epoxide groups, theepoxide equivalent weight is preferably from 400 to 2500, morepreferably from 420 to 2200, with particular preference from 430 to2100, with very particular preference from 440 to 2000, and, inparticular, from 440 to 1900.

[0048] The complementary functional groups described above can beincorporated into the binders in accordance with the customary and knownmethods of polymer chemistry. This can be done, for example, byincorporating monomers which carry the corresponding reactive functionalgroups, and/or with the aid of polymer-analogous reactions.

[0049] Examples of suitable olefinically unsaturated monomers containingreactive functional groups are

[0050] (a1) monomers which carry at least one hydroxyl, amino,alkoxymethylamino, carbamate, allophanate or imino group per molecule,such as

[0051] hydroxyalkyl esters of acrylic acid, methacrylic acid or anotheralpha,beta-olefinically unsaturated carboxylic acid, which are derivedfrom an alkylene glycol which is esterified with the acid, or which areobtainable by reacting the alpha,beta-olefinically unsaturatedcarboxylic acid with an alkylene oxide such as ethylene oxide orpropylene oxide, especially hydroxyalkyl esters of acrylic acid,methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaricacid or itaconic acid, in which the hydroxyalkyl group contains up to 20carbon atoms, such as 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl,3-hydroxybutyl, 4-hydroxybutyl acrylate, methacrylate, ethacrylate,crotonate, maleate, fumarate or itaconate; or hydroxycycloalkyl esterssuch as 1,4-bis(hydroxymethyl)cyclohexane,octa-hydro-4,7-methano-1H-indenedimethanol or methylpropanediolmonoacrylate, monomethacrylate, monoethacrylate, monocrotonate,monomaleate, monofumarate or monoitaconate; reaction products of cyclicesters, such as epsilon-caprolactone and these hydroxyalkyl orhydroxycycloalkyl esters;

[0052] olefinically unsaturated alcohols such as allyl alcohol;

[0053] polyols such as trimethylolpropane monoallyl or diallyl ether orpentaerythritol monoallyl, diallyl or triallyl ether;

[0054] reaction products of acrylic acid and/or methacrylic acid withthe glycidyl ester of an alpha-branched monocarboxylic acid having 5 to18 carbon atoms per molecule, especially a Versatic® acid, or instead ofthe reaction product an equivalent amount of acrylic and/or methacrylicacid, which is then reacted during or after the polymerization reactionwith the glycidyl ester of an alpha-branched monocarboxylic acid having5 to 18 carbon atoms per molecule, especially a Versatic® acid;

[0055] aminoethyl acrylate, aminoethyl methacrylate, allylamine orN-methyliminoethyl acrylate;

[0056] N,N-di(methoxymethyl)aminoethyl acrylate or methacrylate orN,N-di(butoxymethyl)amino-propyl acrylate or methacrylate;

[0057] (meth)acrylamides such as (meth)acrylamide, N-methyl-,N-methylol-, N,N-dimethylol-, N-methoxymethyl-, N,N-di(methoxymethyl)-,N-ethoxymethyl- and/or N,N-di(ethoxyethyl)-(meth)acrylamide;

[0058] acryloyloxy- or methacryloyloxyethyl, -propyl or butylcarbamateor allophanate; further examples of suitable monomers containingcarbamate groups are described in the patents U.S. Pat. No. 3,479,328,U.S. Pat. No. 3,674,838, U.S. Pat. No. 4,126,747, U.S. Pat. No.4,279,833 or U.S. Pat. No. 4,340,497;

[0059] acryloxysilane-containing vinyl monomers, preparable by reactinghydroxy-functional silanes with with epichlorohydrin and then reactingthe reaction product with (meth)acrylic acid and/or hydroxyalkyl estersand/or hydroxycycloalkyl esters of (meth)acrylic acid and/or furtherhydroxyl-containing monomers (a1).

[0060] (a2) Monomers which carry at least one acid group per molecule,such as

[0061] acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid,maleic acid, fumaric acid or itaconic acid;

[0062] olefinically unsaturated sulfonic or phosphonic acids or theirpartial esters;

[0063] mono(meth)acryloyloxyethyl maleate, succinate or phthalate; or

[0064] vinylbenzoic acid (all isomers), alpha-methylvinylbenzoic acid(all isomers) or vinylbenzenesulfonic acid (all isomers).

[0065] (a3) Monomers containing epoxide groups, such as the glycidylester of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid,maleic acid, fumaric acid or itaconic acid, or allyl glycidyl ether.

[0066] They are preferably used to prepare (meth)acrylate copolymers,especially the ones containing glycidyl groups.

[0067] More highly functional monomers of the type described above aregenerally used in minor amounts. For the purposes of the presentinvention, minor amounts of higher-functional monomers are those amountswhich do not lead to crosslinking or gelling of the copolymers, inparticular of the (meth)acrylate copolymers, unless the specific desireis to prepare crosslinked polymeric microparticles.

[0068] Examples of suitable monomer units for introducing reactivefunctional groups into polyesters or polyester-polyurethanes are2,2-dimethylolethyl- or -propylamine blocked with a ketone, theresulting ketoxime group being hydrolyzed again following incorporation;or compounds containing two hydroxyl groups or two primary and/orsecondary amino groups and also at least one acid group, in particularat least one carboxyl group and/or at least one sulfonic acid group,such as dihydroxypropionic acid, dihydroxysuccinic acid,dihydroxybenzoic acid, 2,2-dimethylolacetic acid,2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid,2,2-dimethylolpentanoic acid, α,δ-diaminovaleric acid,3,4-diaminobenzoic acid, 2,4-diaminotoluenesulfonic acid or2,4-diaminodiphenyl ether sulfonic acid.

[0069] One example of introducing reactive functional groups by way ofpolymer-analogous reactions is the reaction of hydroxyl-containingresins with phosgene, resulting in resins containing chloroformategroups, and the polymer-analogous reaction of the with ammonia and/orprimary and/or secondary amines to give resins containing carbamategroups. Further examples of suitable methods of this kind are known fromthe patents U.S. Pat. No. 4,758,632 A1, U.S. Pat. No. 4,301,257 A1 orU.S. Pat. No. 2,979,514 A1.

[0070] The binders of the dual-cure powder slurries of the invention orof the powder slurries of the invention that are curable purely withactinic radiation further comprise on average at least one, preferablyat least two, group(s) having at least one bond per molecule that can beactivated with actinic radiation.

[0071] For the purposes of the present invention, a bond that can beactivated with actinic radiation is a bond which on exposure to actinicradiation becomes reactive and, with other activated bonds of its kind,enters into polymerization reactions and/or crosslinking reactions whichproceed in accordance with free-radical and/or ionic mechanisms.Examples of suitable bonds are carbon-hydrogen single bonds orcarbon-carbon, carbon-oxygen, carbon-nitrogen, carbon-phosphorus orcarbon-silicon single bonds or double bonds. Of these, the carbon-carbondouble bonds are particularly advantageous and are therefore used withvery particular preference in accordance with the invention. For thesake of brevity, they are referred to below as double bonds.

[0072] Accordingly, the group which is preferred in accordance with theinvention comprises one double bond or two, three or four double bonds.If more than one double bond is used, the double bonds can beconjugated. In accordance with the invention, however, it is ofadvantage if the double bonds are present in isolation, in particulareach being present terminally, in the group in question. It is ofparticular advantage in accordance with the invention to use two doublebonds or, in particular, one double bond.

[0073] The dual-cure binder or the binder that is curable purely withactinic radiation contains on average at least one of theabove-described groups that can be activated with actinic radiation.This means that the functionality of the binder in this respect isintegral, i.e., for example, is two, three, four, five or more, ornonintegral, i.e., for example, is from 2.1 to 10.5 or more. Thefunctionality chosen depends on the requirements imposed on therespective dual-cure powder slurry of the invention or the powder slurryof the invention that is curable with actinic radiation.

[0074] If more than one group that can be activated with actinicradiation is used on average per molecule, the groups are structurallydifferent from one another or of the same structure.

[0075] If they are structurally different from one another, this means,in the context of the present invention, that use is made of two, three,four or more, but especially two, groups that can be activated byactinic radiation, these groups deriving from two, three, four or more,but especially two, monomer classes.

[0076] Examples of suitable groups are (meth)acrylate, ethacrylate,crotonate, cinnamate, vinyl ether, vinyl ester, dicyclopentadienyl,norbornenyl, isoprenyl, isopropenyl, allyl or butenyl groups;dicyclopentadienyl, norbornenyl, isoprenyl, isopropenyl, allyl orbutenyl ether groups; or dicyclopentadienyl, norbornenyl, isoprenyl,isopropenyl, allyl or butenyl ester groups, but especially acrylategroups.

[0077] Preferably, the groups are attached to the respective parentstructures of the binders via urethane, urea, allophanate, ester, etherand/or amide groups, but in particular via ester groups. Normally, thisoccurs as a result of customary and known polymer-analogous reactionssuch as, for instance, the reaction of pendant glycidyl groups with theolefinically unsaturated monomers described above that contain an acidgroup, of pendant hydroxyl groups with the halides of these monomers, ofhydroxyl groups with isocyanates containing double bonds such as vinylisocyanate, methacryloyl isocyanate and/or1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)benzene (TMI® fromCYTEC), or of isocyanate groups with the above-describedhydroxyl-containing monomers.

[0078] Alternatively, in the dual-cure powder coating materials, it ispossible to employ mixtures of purely thermally curable binders andbinders that are curable purely with actinic radiation.

[0079] The material composition of the binders has basically no specialfeatures; rather, suitable binders include

[0080] all the binders envisaged for use in powder clearcoat slurriescurable thermally or thermally and with actinic radiation that aredescribed in U.S. patent U.S. Pat. No. 4,268,542 A1 or U.S. Pat. No.5,379,947 A1 and in patent applications DE 27 10 421 A1, DE 195 40 977A1, DE 195 18 392 A1, DE 196 17 086 A1, DE 196 13 547 A1, DE 196 18 657A1, DE 196 52 813 A1, DE 196 17 086 A1, DE 198 14 471 A1, DE 198 41 842A1 or DE 198 41 408 A1, in German Patent Applications DE 199 08 018.6 orDE 199 08 013.5, unpublished at the priority date of the presentspecification, or in European Patent EP 0 652 264 A1;

[0081] all the binders envisaged for use in dual-cure clearcoats thatare described in patent applications DE 198 35 296 A1, DE 197 36 083 A1or DE 198 41 842 A1; or

[0082] all the binders envisaged for use in thermally curable powderclearcoats and described in German Patent Application DE 42 22 194 A1,in the product information bulletin from BASF Lacke+Farben AG,“Pulverlacke”, 1990, or in the BASF Coatings AG brochure “Pulverlacke,Pulverlacke für industrielle Anwendungen”, January 2000.

[0083] In this context, (meth)acrylate addition copolymers are usedpredominantly for the powder slurries that are curable thermally orthermally and with actinic radiation.

[0084] Examples of suitable (meth)acrylate copolymers are the(meth)acrylate copolymers containing epoxide groups, having an epoxideequivalent weight of preferably from 400 to 2500, more preferably from420 to 2200, with particular preference from 430 to 2100, with veryparticular preference from 440 to 2000, and, in particular, from 440 to1900, a number-average molecular weight (determined by gel permeationchromatography using a polystyrene standard) of preferably from 2000 to20,000 and in particular from 3000 to 10,000, and a glass transitiontemperature (T_(g)) of preferably from 30 to 80, more preferably from 40to 70 and in particular from 40 to 60° C. (measured by means ofdifferential scanning calorimetry (DSC), as suitable in particular foruse in thermally curable powder clearcoat slurries (see above) and asdescribed, furthermore, in the patents and patent applications EP 0 299420 A1, DE 22 14 650 B1, DE 27 49 576 B1, U.S. Pat. No. 4,091,048 A1 orU.S. Pat. No. 3,781,379 A1).

[0085] Suitable additional binders for the dual-cure powder slurries ofthe invention, or suitable sole binders for the powder slurries of theinvention that are curable purely with actinic radiation, are thebinders envisaged for use in UV-curable clearcoats, powder clearcoatsand powder slurry clearcoats and described in European PatentApplications EP 0 928 800 A1, EP 0 636 669 A1, EP 0 410 242 A1, EP 0 783534 A1, EP 0 650 978 A1, EP 0 650 979 A1, EP 0 650 985 A1, EP 0 540 884A1, EP 0 568 967 A1, EP 0 054 505 A1 or EP 0 002 866 A1, in GermanPatent Applications DE 198 35 206 A1, DE 197 09 467 A1, DE 42 03 278 A1,DE 33 16 593 A1, DE 38 36 370 A1, DE 24 36 186 A1 or DE 20 03 579 B1, inthe International Patent Applications WO 97/46549 or WO 99/14254, or inU.S. patents U.S. Pat. No. 5,824,373 A1, U.S. Pat. No. 4,675,234 A1,U.S. Pat. No. 4,634,602 A1, U.S. Pat. No. 4,424,252 A1, U.S. Pat. No.4,208,313 A1, U.S. Pat. No. 4,163,810 A1, U.S. Pat. No. 4,129,488 A1,U.S. Pat. No. 4,064,161 A1 or U.S. Pat. No. 3,974,303 A1.

[0086] The preparation of the binders also has no special features as toits method, but takes place with the aid of the customary and knownmethods of polymer chemistry, as described in detail, for example, inthe patent documents recited above.

[0087] Examples of suitable preparation processes for (meth)acrylatecopolymers are described in European Patent Application EP 0 767 185 A1,in German Patents DE 22 14 650 B1 or DE 27 49 576 B1, and in U.S.patents U.S. Pat. No. 4,091,048 A1, U.S. Pat. No. 3,781,379 A1, U.S.Pat. No. 5,480,493 A1, U.S. Pat. No. 5,475,073 A1 or U.S. Pat. No.5,534,598 A1, or in the standard work Houben-Weyl, Methoden derorganischen Chemie, 4^(th) Edition, Volume 14/1, pages 24 to 255, 1961.Suitable reactors for the copolymerization are the customary and knownstirred vessels, cascades of stirred vessels, tube reactors, loopreactors or Taylor reactors, as described, for example, in the patentsand patent applications DE 1 071 241 B1, EP 0 498 583 A1 or DE 198 28742 A1 or in the article by K. Kataoka in Chemical Engineering Science,Volume 50, No. 9, 1995, pages 1409 to 1416.

[0088] The preparation of polyesters and alkyd resins is also described,for example, in the standard work Ullmanns Encyklopädie der technischenChemie, 3^(rd) Edition, Volume 14, Urban & Schwarzenberg, Munich,Berlin, 1963, pages 80 to 89 and pages 99 to 105, and also in thefollowing books: “Résines Alkydes-Polyesters” by J. Bourry, Paris,Dunod, 1952, “Alkyd Resins” by C. R. Martens, Reinhold PublishingCorporation, New York, 1961, and “Alkyd Resin Technology” by T. C.Patton, Interscience Publishers, 1962.

[0089] The preparation of polyurethanes and/or acrylated polyurethanesis also described, for example, in the patent applications EP 0 708 788A1, DE 44 01 544 A1 or DE 195 34 361 A1.

[0090] The binder content of the disperse phase, i.e., of the finelydivided, dimensionally stable constituents, of the powder slurryclearcoats of the invention may vary very widely and depends inparticular on whether they are physically curable, curable thermallywith self-crosslinking and/or curable with actinic radiation. In bothcases, it can be preferably from 20 to 99.99, more preferably from 25 to99.9, with particular preference from 30 to 99.8, with very particularpreference from 35 to 99.75, and, in particular, from 40 to 99.7% byweight, based in each case on the solids content of the powder slurry.In the other cases (curable thermally and/or with actinic radiation andexternally crosslinking), the binder content is preferably from 10 to80, more preferably from 15 to 75, with particular preference from 20 to70, with very particular preference from 25 to 65, and, in particular,from 30 to 60% by weight, based in each case on the solids content ofthe powder slurry clearcoat of the invention.

[0091] The externally crosslinking powder slurry clearcoats of theinvention curable thermally, or thermally and with actinic radiation,comprise at least one crosslinking agent which comprises the reactivefunctional groups complementary to the reactive functional groups of thebinders. Consequently, the skilled worker is easily able to select thecrosslinking agents suitable for a given powder slurry clearcoat.

[0092] Examples of suitable crosslinking agents are

[0093] amino resins, as described for example in Römpp Lexikon Lacke undDruckfarben, George Thieme Verlag, 1998, page 29, “Amino resins”, in thetextbook “Lackadditive” by Johan Bieleman, Wiley-VCH, Weinheim, NewYork, 1998, pages 242 ff., in the book “Paints, Coatings and Solvents”,second completely revised edition, Eds. D. Stoye and W. Freitag,Wiley-VCH, Weinheim, New York, 1998, pages 80 ff., in patents U.S. Pat.No. 4,710,542 A1 or EP 0 245 700 A1, and in the article by B. Singh andcoworkers “Carbamylmethylated Melamines, Novel Crosslinkers for theCoatings Industry” in Advanced Organic Coatings Science and TechnologySeries, 1991, Volume 13, pages 193 to 207;

[0094] carboxyl-containing compounds or resins, as described for examplein the patent DE 196 52 813 A1 or 198 41 408 A1, especiallydodecanedioic acid;

[0095] epoxy-containing compounds or resins, as described for example inpatents EP 0 299 420 A1, DE 22 14 650 B1, DE 27 49 576 B1, U.S. Pat. No.4,091,048 A1 or U.S. Pat. No. 3,781,379 A1;

[0096] blocked polyisocyanates, as described for example in the patentsU.S. Pat. No. 4,444,954 A1, DE 196 17 086 A1, DE 196 31 269 A1, EP 0 004571 A1 or EP 0 582 051 A1;

[0097] beta-hydroxyalkylamides such asN,N,N′,N′-tetrakis(2-hydroxyethyl)adipamide orN,N,N′,N′-tetrakis(2-hydroxypropyl)adipamide; and/or

[0098] tris(alkoxycarbonylamino)triazines, as described in patents U.S.Pat. No. 4,939,213 A1, U.S. Pat. No. 5,084,541 A1, U.S. Pat. No.5,288,865 A1 or EP 0 604 922 A1.

[0099] The crosslinking agent content of the powder coating materialsand powder slurry clearcoats of the invention may likewise vary verywidely and depends on the requirements of the individual case, inparticular on the number of reactive functional groups present. It ispreferably from 1 to 40, more preferably from 2 to 35, with particularpreference from 3 to 30, with very particular preference from 4 to 27,and, in particular, from 5 to 25% by weight, based in each case on thesolids content of the powder slurry clearcoat of the invention.

[0100] In addition to the above-described constituents, the powderslurry clearcoats of the invention may further comprise at least oneadditive. Depending on its physicochemical properties and/or itsfunction, said additive may be present essentially in the finelydivided, dimensionally stable constituents of the powder slurryclearcoats of the invention or essentially in the continuous aqueousphase.

[0101] Examples of suitable additives are

[0102] thermally curable reactive diluents such as positionally isomericdiethyloctanediols or hydroxyl-containing hyperbranched compounds ordendrimers as described in German Patent Applications DE 198 05 421 A1,DE 198 09 643 A1 or DE 198 40 405 A1;

[0103] reactive diluents curable with actinic radiation, such as thosedescribed in Römpp Lexikon Lacke und Druckfarben, George Thieme Verlag,Stuttgart, New York, 1998, on page 491 under the headword “Reactivediluents”;

[0104] crosslinking catalysts such as dibutyltin dilaurate, lithiumdecanoate or zinc octoate, amine-blocked organic sulfonic acids,quaternary ammonium compounds, amines, imidazole and imidazolederivatives such as 2-styrylimidazole, 1-benzyl-2-methylimidazole,2-methylimidazole and 2-butylimidazole, as described in Belgian PatentNo. 756,693, or phosphonium catalysts such as ethyltriphenylphosphoniumiodide, ethyltriphenylphosphonium chloride, ethyltriphenylphosphoniumthiocyanate, ethyltriphenylphosphonium acetate-acetic acid complex,tetrabutylphosphonium iodide, tetrabutylphosphonium bromide andtetrabutylphosphonium acetate-acetic acid complex, as are described, forexample, in U.S. patents U.S. Pat. No. 3,477,990 A1 or U.S. Pat. No.3,341,580 A1;

[0105] thermally labile free-radical initiators such as organicperoxides, organic azo compounds or C—C—cleaving initiators such asdialkyl peroxides, peroxocarboxylic acids, peroxodicarbonates, peroxideesters, hydroperoxides, ketone peroxides, azodinitriles or benzpinacolsilyl ether;

[0106] photoinitiators, as described in Römpp Chemie Lexikon, 9^(th)expanded and revised edition, Georg Thieme Verlag, Stuttgart, Vol. 4,1991, or in Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag,Stuttgart, 1998, pages 444 to 446;

[0107] antioxidants such as hydrazines and phosphorus compounds;

[0108] UV absorbers such as triazines and benzotriphenol;

[0109] light stabilizers such as HALS compounds, benzotriazoles oroxalanilides;

[0110] leveling agents;

[0111] free-radical scavengers and polymerization inhibitors such asorganic phosphites or 2,6-di-tert-butylphenol derivatives;

[0112] slip additives;

[0113] defoamers;

[0114] emulsifiers, especially nonionic emulsifiers such as alkoxylatedalkanols, phenols and alkylphenols, anionic emulsifiers such as alkalimetal salts or ammonium salts of alkanecarboxylic acids, alkanesulfonicacids, and sulfo acids of alkoxylated alkanols and polyols, phenols andalkylphenols;

[0115] wetting agents such as siloxanes, fluorine compounds, carboxylicmonoesters, phosphoric esters, polyacrylic acids and their copolymers,or polyurethanes, as described, for example, in detail in patentapplication DE 198 35 296 A1, especially in conjunction with thepolyurethane-based associative thickeners described below;

[0116] adhesion promoters such as tricyclodecanedimethanol;

[0117] film-forming auxiliaries such as cellulose derivatives;

[0118] flame retardants;

[0119] devolatilizers such as diazadicycloundecane or benzoin;

[0120] water retention agents;

[0121] free-flow aids;

[0122] transparent fillers such as pyrogenic silica or nanoparticlesbased on silica, titanium dioxide or zirconium dioxide;

[0123] rheology control additives (thickeners), such as those known frompatents WO 94/22968, EP-A-0 276 501, EP-A-0 249 201 or WO 97/12945;crosslinked polymeric microparticles, such as those disclosed, forexample, in EP-A-0 008 127; inorganic sheet silicates such asaluminum-magnesium silicates, sodium-magnesium andsodium-magnesium-fluorine-lithium sheet silicates of the montmorillonitetype; silicas such as Aerosils; or synthetic polymers having ionicand/or associative groups, such as polyvinyl alcohol,poly(meth)-acrylamide, poly(meth)acrylic acid, polyvinyl-pyrrolidone,styrene-maleic anhydride copolymers or ethylene-maleic anhydridecopolymers and their derivatives or polyacrylates; or polyurethane-basedassociative thickeners, as described in Römpp Lexikon Lacke undDruckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998,“Thickeners”, pages 599 to 600, and in the textbook “Lackadditive” byJohan Bieleman, Wiley-VCH, Weinheim, New York, 1998, pages 51 to 59 and65; especially combinations of ionic and nonionic thickeners, asdescribed in patent application DE 198 41 842 A1 for establishing apseudoplastic behavior, or the combination of polyurethane-basedassociative thickeners and polyurethane-based wetting agents, as isdescribed in detail in German Patent Application DE 198 35 296 A1.

[0124] Further examples of suitable additives are described in thetextbook “Lackadditive” by Johan Bieleman, Wiley-VCH, Weinheim, NewYork, 1998. They are employed in the customary and known amounts.

[0125] The preparation of the powder slurry clearcoats of the inventionby the process of the invention is based on conventional processes forpreparing powder slurry clearcoats.

[0126] In a first preferred variant, the powder slurry clearcoats of theinvention are prepared from the constituents described above essentiallyas described in Patent Applications DE 195 40 977 A1, DE 195 18 392 A1,DE 196 17 086 A1, DE-A-196 13 547, DE 196 18 657 A1, DE 196 52 813 A1,DE 196 17 086 A1, DE-A-198 14 471 A1, DE 198 41 842 A1 or DE 198 41 408A1 in detail.

[0127] In this case, a powder coating material known per se is convertedinto a powder slurry by means of wet milling in water or an aqueousmedium, i.e., a mixture of water and at least one of the additivesdescribed above.

[0128] In another preferred variant of preparing the powder slurryclearcoats of the invention, the constituents described above areemulsified in an organic solvent to give an emulsion of the oil-in-watertype, after which the organic solvent is removed; as a result of this,the emulsified droplets solidify and a powder slurry results. The powderslurry is then subjected to wet milling.

[0129] In a third preferred variant of preparing the powder slurryclearcoats of the invention, a liquid melt of the constituents describedabove is introduced into an emulsifying apparatus, preferably with theaddition of water and stabilizers, and the emulsion obtained is cooledand filtered, giving a powder slurry. In order to achieve a high qualityof mixing, it is essential to carry out mixing in the melt withoutsolvent. Accordingly, the polymeric constituents are fed into thedispersing apparatus in the form of viscous resin melts. The powderslurry is then wet milled.

[0130] For the process of the invention and the powder slurry clearcoatsof the invention it is essential that the above-described adducts foruse in accordance with the invention and, if desired, theabove-described solvents of high solvency are added to the powderslurries prior to wet milling. Wet milling of the adducts for use inaccordance with the invention and, if desired, of the solvents with theother, above-described constituents results in the powder slurryclearcoats of the invention.

[0131] In terms of method, the wet milling operation has no specialfeatures but instead is carried out with the aid of customary and knownapparatus such as stirred mills, for example.

[0132] Preferably, the resultant powder slurry clearcoats of theinvention are filtered after wet milling. This is done using thecustomary and known filtration equipment and filters, as also suitablefor filtering known powder slurries. The mesh size of the filters mayvary widely and is guided primarily by the particle size and by theparticle size distribution of the particles in the suspension. Theskilled worker will therefore easily be able to determine theappropriate filters on the basis of this physical parameter. Examples ofsuitable filters are bag filters. These are available commercially underthe brand names Pong® or Cuno®. It is preferred to use bag filtershaving mesh sizes from 10 to 50 μm, examples being Pong® 10 to Pong® 50.

[0133] The powder slurry clearcoats of the invention are used to produceclearcoat finishes, especially as part of multicoat color and/or effectfinishes on primed and unprimed substrates.

[0134] The clearcoat finish of the invention or the multicoat colorand/or effect finish comprising the clearcoat finish of the invention isused in particular in automotive finishing, in the coating of interiorand exterior constructions, in the coating of furniture, doors andwindows, and in industrial coating, including coil coating and containercoating, appropriate substrates being all those which are known andcustomary in these technical fields, made of metal, plastic, glass,wood, textile, leather, natural stone, synthetic stone, concrete, cementor composites of these materials, preference being given to theelectrically conductive substrates.

[0135] The multicoat color and/or effect finish of the invention ispreferably preparable on a substrate by

[0136] (1) applying a surfacer or functional coating material to acathodically deposited and thermally cured electrodeposition coating, orwet-on-wet to a cathodically deposited, uncured or only part-curedelectrodeposition coating film, and then

[0137] (2) subjecting the resultant surfacer film or functional film, onits own, to curing thermally, or thermally and with actinic radiation,or, together with the electrodeposition coating film, to curingthermally, or thermally and with actinic radiation, to give the surfacercoat, antistonechip primer, or functional coat,

[0138] (3) applying a basecoat, especially an aqueous basecoat, to thesurfacer coat, antistonechip primer or functional coat, to give abasecoat film,

[0139] (4) flashing off or drying the basecoat film without completelycrosslinking it, or—alternatively—curing it physically, thermally and/orwith actinic radiation, to give the basecoat,

[0140] (5) applying at least one powder slurry clearcoat of theinvention to the basecoat film or—alternatively—to the basecoat, andthen

[0141] (6) curing the basecoat film and the resulting powder slurryclearcoat film(s) together, thermally and/or with actinic radiation,or—alternatively—curing the powder slurry clearcoat film(s), on its(their) own, thermally and/or with actinic radiation, to give thebasecoat and the clearcoat(s).

[0142] In a further preferred variant, the multicoat color and/or effectfinish of the invention is preparable on a substrate by

[0143] (1) applying a surfacer or functional coating material to acathodically deposited and thermally cured electrodeposition coating,and then

[0144] (2) flashing off or drying the resulting surfacer film orfunctional film, without completely crosslinking it,

[0145] (3) applying a basecoat material, especially an aqueous basecoatmaterial, to the surfacer film or functional film, to give a basecoatfilm,

[0146] (4) flashing off or drying the basecoat film, without completelycrosslinking it,

[0147] (5) applying at least one powder slurry clearcoat of theinvention to the basecoat film, and then

[0148] (6) curing the surfacer film or functional film, the basecoatfilm and the powder slurry clearcoat film(s) together, thermally and/orwith actinic radiation, to give the surfacer coat, antistonechip primeror functional coat, the basecoat, and the clearcoat(s).

[0149] Examples of suitable cathodic electrodeposition coating materialsand also, where appropriate, of wet-on-wet processes are described inJapanese Patent Application 1975-142501 (Japanese Laid-OpenSpecification JP 52-065534 A2, Chemical Abstracts No. 87: 137427) or inthe patents U.S. Pat. No. 4,375,498 A1, U.S. Pat. No. 4,537,926 A1, U.S.Pat. No. 4,761,212 A1, EP 0 529 335 A1, DE 41 25 459 A1, EP 0 595 186A1, EP 0 074 634 A1, EP 0 505 445 A1, DE 42 35 778 A1, EP 0 646 420 A1,EP 0 639 660 A1, EP 0 817 648 A1, DE 195 12 017 C1, EP 0 192 113 A2, DE41 26 476 A1 or WO 98/07794.

[0150] Examples of suitable surfacers, especially aqueous surfacers,which are also referred to as antistonechip primers or functionalcoatings, are described in patents U.S. Pat. No. 4,537,926 A1, EP 0 529335 A1, EP 0 595 186 A1, EP 0 639 660 A1, DE 44 38 504 A1, DE 43 37 961A1, WO 89/10387, U.S. Pat. No. 4,450,200 A1, U.S. Pat. No. 4,614,683 A1or WO 94/26827.

[0151] Examples of suitable basecoat materials, preferably aqueousbasecoat materials, especially polyurethane-based aqueous basecoatmaterials, are known from patents EP 0 089 497 A1, EP 0 256 540 A1, EP 0260 447 A1, EP 0 297 576 A1, WO 96/12747, EP 0 523 610 A1, EP 0 228 003A1, EP 0 397 806 A1, EP 0 574 417 A1, EP 0 531 510 A1, EP 0 581 211 A1,EP 0 708 788 A1, EP 0 593 454 A1, DE-A-43 28 092 A1, EP 0 299 148 A1, EP0 394 737 A1, EP 0 590 484 A1, EP 0 234 362 A1, EP 0 234 361 A1, EP 0543 817 A1, WO 95/14721, EP 0 521 928 A1, EP 0 522 420 A1, EP 0 522 419A1, EP 0 649 865 A1, EP 0 536 712 A1, EP 0 596 460 A1, EP 0 596 461 A1,EP 0 584 818 A1, EP 0 669 356 A1, EP 0 634 431 A1, EP 0 678 536 A1, EP 0354 261 A1, EP 0 424 705 A1, WO 97/49745, WO 97/49747, EP 0 401 565 A1or EP 0 817 684, column 5, lines 31 to 45.

[0152] These aqueous basecoat materials may also be used as functionalcoating materials for producing functional films and functional coats.

[0153] The resultant clearcoats or multicoat color and/or effectfinishes of the invention may further be coated with a scratchproofcoating of an organically modified ceramic material, as availablecommercially under the brand name ORMOCER®, for example.

[0154] In general, the coating materials are applied in a wet filmthickness such that curing thereof results in coatings having the coatthicknesses which are necessary and advantageous for their functions. Inthe case of the electrodeposition coating, these thicknesses are from 5to 40, preferably from 10 to 35, with particular preference from 12 to30 and in particular from 15 to 25 μm; in the case of the surfacer coat,antistonechip primer or functional coats they are from 10 to 60,preferably from 11 to 55, with particular preference from 12 to 50 andin particular from 13 to 45 μm; in the case of the basecoat they arefrom 5 to 50, preferably from 5 to 40, with particular preference from 5to 30 and in particular from 10 to 25 μm; and in the case of theclearcoat of the invention they are from 10 to 100, preferably from 15to 80, with particular preference from 20 to 75 and in particular from25 to 70 μm. However, in the multicoat finish of the invention thefunctional coat may have only a coat thickness of from 20 to 50% of theoverall coat thickness of functional coat and basecoat.

[0155] Although the powder slurry clearcoats of the invention are alsosuitable for use outside of automobile finishing, their principalindustrial end use lies within said sector since it is here that theirspecial advantages are manifested quite obviously. The substrates aretherefore motor vehicle bodies, especially automobile bodies, and alsoparts thereof, such as doors, engine hoods, wings, trunk lid spoilers,sills or wind deflectors, for example.

[0156] These substrates consist in particular of steel or aluminum. Themetal surfaces may in this case carry primers. In the case of aluminum,for example, there may be an oxide layer produced by anodic oxidation(Eloxal® process). In the case of steel, there is normally a thermallycured cathodic electrodeposition coating. However, it is also possibleto use a cathodic electrodeposition coating film which has not beenthermally cured but is merely dried or partially cured.

[0157] The powder slurry clearcoats of the invention can be appliedusing the methods known from liquid coating technology. In particular,they can be applied by means of spraying processes. Preferably, they areapplied by electrostatic painting of the exterior body parts followed bypneumatic spraying (compressed-air spraying) of the interior body parts.

[0158] The electrostatic painting can take place by means of anelectrostatic spraying gap, an electrostatic spraying bell, or anelectrostatic spraying disk.

[0159] Furthermore, the electrostatic painting may take place by meansof electrostatically assisted mechanical atomization. Preferably, thisis carried out with the aid of electrostatic high-speed rotary disks orhigh-speed rotary bells.

[0160] The pneumatic spraying or compressed-air painting, as well, hasno special features as to its method, but can be carried out by hand orusing customary and known automatic painting equipment or paint robots.

[0161] For further details, reference is made here to Römpp LexikonLacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998,page 186: “Electrostatic painting”, page 187: “Electrostatic sprayguns”, “Electrostatic Spraying”, and page 165: “Compressed-airspraying”.

[0162] Preferably, application is carried out under illumination withvisible light having a wavelength of more than 550 μm or in the absenceof light if the powder slurry clearcoats of the invention are curable(inter alia) with actinic radiation. By this means, material alterationor damage to the coating material to be used in accordance with theinvention and to the overspray is avoided.

[0163] Of course, these application processes can also be employed forthe application of additional coating films, provided the coatingmaterials concerned are not electrodeposition coating materials.

[0164] The method of curing the applied electrodeposition coating films,surfacer films or functional films, basecoat films and clearcoat filmsof the invention has no special features but instead takes place withthe aid of the customary and known processes and apparatus.

[0165] For physical curing, it is not necessary per se to take anyspecial measures, although physical curing may be assisted byatmospheric oxygen, by heat, or by exposure to actinic radiation.

[0166] Thermal curing may be carried out after a certain resting time orflash-off time. It may last for from 30 seconds to 2 hours, preferablyfrom 1 minute to 1 hour, and in particular from 1 minute to 45 minutes.The resting time is used, for example, for leveling and degassing of thefilms and for the evaporation of volatile constituents such as anysolvents and/or water that may still be present. Flashing-off can beaccelerated by an elevated temperature, though still below that forcuring, and/or by reduced atmospheric humidity.

[0167] The thermal curing, for example, takes place by heating in aconvection oven or irradiation with IR and/or NIR lamps. As in the caseof curing with actinic radiation, the thermal curing may also take placein stages. Advantageously, thermal curing takes place at temperaturesfrom 100 to 180° C.

[0168] In the case of curing with actinic radiation, it is preferred toemploy a dose of from 1000 to 3000, preferably from 1100 to 2900, withparticular preference from 1200 to 2800, with very particular preferencefrom 1300 to 2700, and in particular from 1400 to 2600, mJ/cm². Ifdesired, this curing may be supplemented by actinic radiation from otherradiation sources. In the case of electron beams, it is preferred tooperate under an inert gas atmosphere. This can be ensured, for example,by supplying carbon dioxide and/or nitrogen directly to the surface ofthe powder slurry coat. In the case of curing with UV radiation as well,it is possible to operate under inert gas in order to prevent theformation of ozone.

[0169] Curing with actinic radiation is carried out using the customaryand known radiation sources and optical auxiliary measures. Examples ofsuitable radiation sources are flashlights from the company VISIT,high-pressure or low-pressure mercury vapor lamps, with or without leaddoping in order to open a radiation window of up to 405 nm, or electronbeam sources. The arrangement of these sources is known in principle andmay be adapted to the circumstances of the workpiece and the processparameters. In the case of workpieces of complex shape, as provided forautomobile bodies, those regions not accessible to direct radiation(shadow regions), such as cavities, folds and other structuralundercuts, may be (partially) cured using point, small-area or all-roundemitters, in combination with an automatic movement apparatus for theirradiation of cavities or edges.

[0170] The equipment and conditions for these curing methods aredescribed, for example, in R. Holmes, U.V. and E.B. Curing Formulationsfor Printing Inks, Coatings and Paints, SITA Technology, Academic Press,London, United Kingdom, 1984.

[0171] Full curing here may take place in stages, i.e., by multipleexposure to light or actinic radiation. It can also take place inalternation; in other words, by curing alternately with UV radiation andelectron beams.

[0172] In the case of dual cure, thermal curing and curing with actinicradiation can be employed simultaneously or in succession. If the twocuring methods are used in succession, it is possible, for example, tocommence with thermal curing and end with curing with actinic radiation.In other cases, it may prove advantageous to commence and to end withcuring with actinic radiation.

[0173] The powder slurry coat of the invention is preferably cured inthe molten state using the above-described methods.

[0174] Overall, the processes of the invention for producing themulticoat effect finishes of the invention offer the extremelyenvironmentally and economically advantageous and significantpossibility of realizing coating systems on a purely aqueous basiswithout emission of volatile organic substances.

[0175] The clearcoats and multicoat color and/or effect finishesobtained in the manner of the invention are distinguished by very goodsubstrate adhesion, very good intercoat adhesion, outstanding corrosionprotection, very good protection against stone chipping and othermechanical damage, and a very good overall visual appearance, especiallyas regards depth of color, metallic effect, dichroic effect, and D.O.I.(distinctness of the reflected image), and high scratch, chemical andweathering resistance. In particular, however, the clearcoat finishes ofthe invention no longer exhibit surface defects such as depressions,craters or agglomerates.

[0176] The bodies of the invention coated accordingly therefore impart aparticularly high overall esthetic impression and have a particularlylong service life.

EXAMPLE

[0177] The Preparation of a Multicoat Effect Finish of the InventionUsing a Powder Slurry of the Invention

[0178] For the example, a powder coating material was first prepared, asdescribed in German Patent Application DE 196 13 547 A1, from 77.4 partsby weight of a methacrylate copolymer formed from methyl methacrylate,glycidyl methacrylate, n-butyl acrylate and styrene, 19.4 parts byweight of dodecanedioic acid, 2 parts by weight of a commercial UVabsorber (Ciba® CGL 1545), 1 part by weight of the commercial lightstabilizer Tinuvin® 123, and 0.25 part by weight of the commercialantiozidant Irgafos® PEPQ.

[0179] This powder coating material was dispersed in water in accordancewith the experimental procedure specified in German Patent ApplicationDE 196 13 547 A1, column 6, to give a powder slurry.

[0180] Prior to the wet milling of the powder slurry in a customary andknown stirred mill, it was admixed with the make-up composition statedin the table. Wet milling then gave the powder slurry clearcoat of theinvention with an average particle size of from 3 to 5 μm.

[0181] Prior to application, the powder slurry clearcoat of theinvention was further filtered through a bag filter with a mesh size of50 μm.

[0182] The table gives an overview of the nature and amount of theconstituents used. TABLE The preparation of the powder slurryConstituent Parts by weight Predispersion: DI water^(a)) 42 Disperse AidW22^(b)) 1.03 Triton X100^(c)) 0.02 Dimethylethanolamine 0.08 RM 8^(d))0.9 Powder coating material 28 Make-up Composition: DI water^(a)) 17.49RM 8^(d)) 0.7 Byk 333^(g)) 0.05 Triton X100^(c)) 0.18 Pluriol ® 600^(f))0.155 Solvenon ® IPP^(g)) 0.31

[0183] To produce the multicoat finish of the invention, test panelsmeasuring 10 cm×20 cm were produced in a customary and known manner. Forthis purpose, steel panels (body panels) coated with a customary andknown cathodically deposited and baked electrodeposition coating (EDC)were coated with a commercially customary thin-film surfacer (Ecoprime®from BASF Coatings AG), after which the resulting surfacer film wasflashed off at 20° C. for five minutes at a relative atmospherichumidity of 65% and then dried at 80° for five minutes in a convectionoven. After that, the surfacer coats had a dry film thickness of 15 μm.

[0184] After the test panels had cooled to 20° C., a commerciallycustomary aqueous basecoat (Ecostar® from BASF Coatings AG) was appliedand the coated panels were flashed off at 20° C. for five minutes at arelative atmospheric humidity of 65% and then dried at 80° C. for fiveminutes in a convection oven, so that the dried basecoat films had a dryfilm thickness of approximately 15 μm.

[0185] After the test panels had again been cooled to 20° C., thebasecoats were overcoated with the powder slurry of the invention. Theresultant powder slurry clearcoat films were flashed off at 20° C. forthree minutes at a relative atmospheric humidity of 65% and dried at 60°C. for five minutes in a convection oven.

[0186] Following the application of all three coats, they were bakedtogether at 155° C. for 30 minutes to give the multicoat finish of theinvention. Its clearcoat of the invention had a film thickness of 40 μm.It was highly glossy and possessed outstanding solvent resistance (morethan 100 double strokes in the methyl ethyl ketone test without damage)and good humidity resistance. The intercoat adhesion was very good. Theclearcoat finish of the invention was resistant to scratching,chemicals, and weathering. It had no surface defects such as poppingmarks, craters, depressions, or agglomerates.

What is claimed is:
 1. A powder clearcoat dispersion (powder slurryclearcoat) preparable by dispersing a powder clearcoat in an aqueousmedium and wet milling the resulting powder slurry, at least one adductof ethylene oxide and/or propylene oxide with at least one glycol beingadded to the powder slurry prior to wet milling.
 2. The powder slurryclearcoat as claimed in claim 1, characterized in that said glycolcomprises ethylene glycol, 1,3- and/or 1,2-propylene glycol or 1,2-,1,3- and/or 1,4-butylene glycol.
 3. The powder slurry clearcoat asclaimed in claim 2, characterized in that 1,2- and/or 1,3-propyleneglycol is used.
 4. The powder slurry clearcoat as claimed in claim 3,characterized in that the adduct of propylene oxide with 1,2- and/or1,3-propylene glycol (polypropylene glycol) is used.
 5. The powderslurry clearcoat as claimed in claim 4, characterized in that thenumber-average molecular weight of the polypropylene glycol is from 350to 1000 daltons.
 6. The powder slurry clearcoat as claimed in any ofclaims 1 to 5, characterized in that the adducts are used in an amountof from 0.01 to 2.0% by weight, based on the solids content of therespective powder slurry clearcoat.
 7. The powder slurry clearcoat asclaimed in any of claims 1 to 6, characterized in that together with theadduct from 0.1 to 1.9 parts by weight of at least one organic solventof high solvency are used per 100 parts by weight of solids of thepowder slurry clearcoat.
 8. The powder slurry clearcoat as claimed inany of claims 1 to 7, characterized in that it is curable physically orthermally and/or with actinic radiation.
 9. The powder slurry clearcoatas claimed in any of claims 1 to 8, characterized in that it ispseudoplastic.
 10. The use of the powder slurry clearcoat as claimed inany of claims 1 to 9 to produce clearcoat finishes, especially as partof multicoat color and/or effect finishes.
 11. A multicoat color and/oreffect finish preparable on a substrate by (1) applying a surfacer orfunctional coating material to a cathodically deposited and thermallycured electrodeposition coating, or wet-on-wet to a cathodicallydeposited, uncured or only part-cured electrodeposition coating film,and then (2) subjecting the resultant surfacer film or functional film,on its own, to curing thermally, or thermally and with actinicradiation, or, together with the electrodeposition coating film, tocuring thermally, or thermally and with actinic radiation, to give thesurfacer coat, antistonechip primer, or functional coat, (3) applying abasecoat, especially an aqueous basecoat, to the surfacer coat,antistonechip primer or functional coat, to give a basecoat film, (4)flashing off or drying the basecoat film without completely crosslinkingit, or—alternatively—curing it physically, or thermally and/or withactinic radiation, to give the basecoat, (5) applying at least onepowder slurry clearcoat of the invention to the basecoat filmor—alternatively—to the basecoat, and then (6) curing the basecoat filmand the resulting powder slurry clearcoat film(s) together, thermally,or thermally and with actinic radiation, or—alternatively—curing thepowder slurry clearcoat film(s), on its (their) own, thermally and/orwith actinic radiation, to give the basecoat and the clearcoat(s),characterized in that said powder slurry clearcoat is a powder slurryclearcoat as claimed in any of claims 1 to
 9. 12. A multicoat colorand/or effect finish preparable on a substrate by (1) applying asurfacer or functional coating material to a cathodically deposited andthermally cured electrodeposition coating, and then (2) flashing off ordrying the resulting surfacer film or functional film, withoutcompletely crosslinking it, (3) applying a basecoat material, especiallyan aqueous basecoat material, to the surfacer film or functional film,to give a basecoat film, (4) flashing off or drying the basecoat film,without completely crosslinking it, (5) applying at least one powderslurry clearcoat to the basecoat film, and then (6) curing the surfacerfilm or functional film, the basecoat film and the powder slurryclearcoat film(s) together, thermally, and/or with actinic radiation, togive the surfacer coat, antistonechip primer or functional coat, thebasecoat, and the clearcoat(s), characterized in that said powder slurryclearcoat is a powder slurry clearcoat as claimed in any of claims 1 to9.
 13. The use of adducts of ethylene oxide and/or propylene oxide withglycols for preventing surface defects in clearcoat finishes producedfrom powder slurry clearcoats.